On the behavior of micro-spheres in a hydrogen pellet target

A pellet target produces micro-spheres of different materials, which are used as an internal target for nuclear and particle physics studies. We will describe the pellet hydrogen behavior by means of fluid dynamics and thermodynamics. In particular one aim is to theoretically understand the cooling effect in order to find an effective method to optimize the working conditions of a pellet target. During the droplet formation the evaporative cooling is best described by a multi-droplet diffusion-controlled model, while in vacuum, the evaporation follows the (revised) Hertz-Knudsen formula. Experimental observations compared with calculations clearly indicated the presence of supercooling, the effect of which is discussed as well.Comment: 22 pages, 8 figures (of which two are significantly compressed for easier download

Numerical modeling of shock-sensitivity experiments

The Forest Fire rate model of shock initiation of heterogeneous explosives has been used to study several experiments commonly performed to measure the sensitivity of explosives to shock and to study initiation by explosive-formed jets. The minimum priming charge test, the gap test, the shotgun test, sympathetic detonation, and jet initiation have been modeled numerically using the Forest Fire rate in the reactive hydrodynamic codes SIN and 2DE

Quasilinear systems, semigroups, and nonlinear coupling

It is known that the semigroup S(t) corresponding to the sum A + B of two non-commuting generators, each having semigroups S/sub A/(t), respectively S/sub B/(t), is given by the Trotter product S/sub A/(t)*S/sub B/(t) = lim n..-->..infinity(S/sub A/(t/n)S/sub B/(t/n))/sup n/ provided the latter converges. We apply this principle in treating a quasilinear system with nonlinear coupling. The conjecture is that some hydrodynamic systems may have semigroups. 9 refs

Using semigroups and the Trotter product formula to solve quasi-linear systems

A quasi-linear system with linear coupling terms is treated. An approximate system for which the Trotter product of constituent semigroups converges is solved. Then it is shown that the approximate solutions converge to a solution of the original system, and that the resulting solution operator is a semigroup. Remarks are made about a nonlinearly coupled system. 12 references